In short, quantitative easing is likely to induce what the late MIT economist Rudiger Dornbusch described as "exchange rate overshooting" - a large and abrupt shift in the spot exchange rate that occurs in order to align long-term equilibrium in the market for goods and services with short-term equilibrium in the capital markets.
This adjustment is depicted in the diagram below. In response to the monetary shock, a modest but long-term depreciation in the dollar (a rise in the U.S. dollar price of foreign currency) is required, depicted by the blue line. However, since nominal interest rates in the U.S. actually decline, ongoing equilibrium in the capital market requires that the U.S. dollar must be expected to appreciate over time by enough to offset the lost interest. As a result, quantitative easing is likely to result in an abrupt "jump depreciation" of the U.S. dollar (that is, a spike in the value of foreign currencies).
My impression is that Ben Bernanke has little sense of the damage he is about to provoke. A central banker who talks about throwing money from helicopters is not only arrogant but foolish. Nearly a century ago, the great economist Ludwig von Mises observed that massive central bank easing is invariably a form of cowardice that attempts to avoid the need to restructure debt or correct fiscal deficits, avoiding wiser but more difficult choices by instead destroying the value of the currency.